A 12-year-old girl was in police custody Thursday after a shooting at Salvador Castro Middle School injured four students.

The gunfire erupted in a classroom at the school in the Westlake neighborhood shortly after the opening bell and caused numerous students to run from the area, according to Los Angeles police Officer Drake Madison.

When authorities responded around 8:55 a.m., they found a 15-year-old boy with a gunshot wound to the head and a 15-year-old girl shot in the wrist and three others with minor injuries.

The boy, who was shot in the temple, was in stable condition Thursday afternoon, and was expected to fully recover, according to Dr. Carl Chudnofsky, of L.A. County-USC Medical Center. The girl, who was shot in the left wrist, was in fair condition.

Three others — a 30-year-old woman, an 11-year-old boy and a 12-year-old girl — also suffered minor injuries, including two from gunshots, health officials said.